Apparatus for embossing leatherlike materials



July 4, 1950 v J, MASON HAL 2,514,213

APPARATUS FOR EMBOSSING LEATHER-LIKE MATERIALS Filed Dec. 11, 1946 IN v E. N "r o w. cJOHN l4. MASON ANV PAQIC P. C1215! ATTORNEYS Patented July 4, l56

UNITED STATES PATENT GFFICE APPARATUS FOR EMBOSSING LEATHER- LIKE MATERIALS John K. Mason, Everett, and Park P. Crisp, Akron, Ohio, assignors to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio Application December 11, 1946, Serial No. 715,578

1 Claim. (Cl. 18-10) This invention relates to artificial leathers or leather-like materials, especially to apparatus for continuously embossing artificial leathers and similar materials to give them more realistic feel and appearance.

Heretofore, artificial leathers have been made by various processes and then, as a separate operation in many instances, the artificial leathers have been given the desired embossed finish. These artificial leather sheets have been from as low as about .01 inch in thickness to .25 of an inch in thickness, approximately, and they have had considerable fields of use, such as upholstery covering, luggage materials, etc, in which the artificial leathers generally serve as a replacement for natural leather. These leathers have, in general, comprised flexible vinyl resins of a class described hereafter in more detail.

The operation of embossing artificial leathers, as usually performed heretofore, has included the steps of reheating a previously-formed artificial leather sheet and then compressing it between suitable platens wherein one platen has the desired embossed design formed thereon, and the second platen serves to force the heated artificial leather up against the embossing platen to form the desired design. In some instances, artificial leathers have been continuously embossed by means of metal embossing rolls used in conjunction with paper back-up rolls. In that case, the paper roll is formed from a plurality of laminations of paper of a suitable composition and the metal embossing roll, which is usually of the same diameter as the paper roll, is pressed against the paper roll and the rolls are rotated so that the paper roll is forced to assume a contour which mates with the surface of the embossing roll. Then the rolls are separated slightly and the heated artificial leather sheet is rolled between such rollers with the paper backing roll serving to force the artificial leather sheet tightly up against the embossing roll and into the design, or embossing recesses formed thereon. This action of the paper backing roll normally forms indentations in the back of the artificial leather and calls for careful adjustment of the relative circumferential positions of the rolls since the peripheral surfaces of the rolls must be exactly mated in order to obtain the desired embossing and backup action. Then, for each difierent type of embossed design desired, a special, and mated, paper back-up roll must be provided. Obviously, both of the embossing processes outlined above have not been completely satisfactory be-v cause the platen method of embossing artificial leather is quite costly and slow. Also, such embossing procedure involves appreciable labor costs. due to its more or less batch type of operation. Use of paper covered back-up rolls also is objectionable since a variety of rolls must be used to produce the variety of embossed designs desired since the paper rolls must be exactly mated with the contour of the metal embossing rolls. Then, too, the paper covered back-up rolls have a limited life at the elevated temperatures ordinarily required for embossing operations.

The general object of the present invention is to avoid and overcome the foregoing, and other disadvantages of and objections to known procedures for embossing artificial leathers and to provide an embossing apparatus which is char acterized by its continuous, low-cost operation.

Another object of the invention is to provide a rubber covered back-up roll for embossing operations, which roll is adapted to be used with any of a number of metal embossing rolls.

A further object of the invention is to provide a rubber covered back-up roll for embossing operations, wherein the rubber covered roll is crowned slightly at its center to give desired pressures at the center of the embossing rolls.

A further object of the invention is to provide special cooling means for a rubber covered backup roll whereby the rubber is not overvulcanized at the high operating temperatures required for embossing artificial leather in accordance with the invention.

The foregoing, and other objects and advantages of the invention, which will be made apparent as the specification proceeds, are achieved, broadly speaking, by the provision of suitable apparatus for kneading thermoplastic material to a temperature of above 300 F. so as to render the material suitably plastic for calendering operations, calendering or rolling the heated thermoplastic material into a continuous thin sheet, immediately embossin the design upon one surface of the moving sheet of thermoplastic'material, and coolin a resilient back-up surface which is used to support the thermoplastic materialduring its embossing operation.

Reference now is made to the accompanying drawings, wherein:

Fi 1 is a diagrammatic section of apparatus for practicing the principles of the invention; v Fig. 2 is a front elevation. of a pair of embossing rolls constructed in accordance with the invention; and

Fig. 3 is an elevation of the rubber covered back-up roll shown in Fig, 2, with the crown of such :back-roll being shown in somewhat exaggerated form.

Attention now is directed to the details of the construction shown in the drawing, and conventional means, such as a calender I is shown for heating up and rendering plastic the material used in forming the artificial leather sheet to be processed in accordance with the invention. The material used in forming artificial leather in accordance with the invention may be any conventional thermoplastic resinous material; such as polymeric vinyl resin which may be either a polymer of vinyl chloride or copolymers thereof with vinyl acetate, vinylidene chloride, and the like; and the modified polyvinyl acetate resins, such as the polyvinyl formals, acetals, butyrals, acetatebutyrals, etc.

One specific composition. which has been used very satisfactorily in the past has been compounded as follows:

Parts Geon 202 100 Dibutyl sebacate 30 Butaprene NSP 13 Calcium stearate 3 The foregoing compound, or any suitable thermoplastic material selected and which may have plasticizers or other ingredients added to it, is mixed or plasticized on any conventional means, which may comprise Banbury mixers, mixing mills, extrusion devices, or other means and then this composition indicated by the numeral II, is deposited between rolls l2 and I3 ofthe calender 10 which forms the material I I into a sheet [4 which is led around the rolls l5 and I8 of the calender l0. Then, as a special feature of the invention, the hot thermoplastic sheet I4 is immediately led between an embossing roll I! and a rubber covered back-up roll l8, Which rolls IT and. I8 are placed immediately adjacent the i calender 10. (The material forming the sheet l4;

when calendered, is normally at a temperature in excess of about 300 F. at which temperature the-material is sufficiently plastic that it will take any shape. to which it is forced by the pressureapplied to it. Due to the kneading action of the calender Hi, the material ll still is at a temperature above 300 F. when it leaves the calender l0: Fig. 1 shows that a water tank [9 isprovided immediately below the roll 18 and that the roll l8 dips into such tank for a purpose which will be made more clear-hereinafter.

Turning now to the details of the pair of embossing rolls l! and I8, Fig. 2 shows that the roll I?! is journalled in suitable bearing blocks 2! that are adjustably received in a pair of spaced vertically extending columns 22 that are associated with and carried by suitable frame members 23. The columns 22 are connected by a tie bar 24 which maintains them in fixed lateral relation. The vertical positions of the bearing blocks 2! are controlled by air cylinders 25, or other adjustable pressure means which are connected to the bearing blocks 2! by plungers 26and which are secured to the columns 22. The bearing blocks 2|, are guided for vertical movement by pins 21 that extend from the bearing blocks out through vertically directed slots 28 formed in the columns 22. Then conventional means (not shown) connect the cylinders 25so that they operate as a unit and can be used to set the rolls I! and 18 with any desired gap between them and with a desired pressure being exerted by the roll I! on the roll l8. Roll l8 may be journalled in bearing blocks 29 that are removably secured in the lower end of the columns 22. Cover plates 30 are removably secured to the forward surfaces of the columns 22 by bolts 30a so that the cover plates can be removed to permit the rolls l7 and Hi to be changed, when desired. One suitable pressure for 60 inch rolls has been 6,000 pounds, and ordinarily sheets of approximately 54 inches width are formed on such rolls. Fig. 2 shows that a suitable embossing design D is formed on the surface of the roll IT. This embossing design is cut into the roll ll; in any conventional manner and is of the depth and shape required so as to produce the desired figures or design on the surface of the artificial leather product.

An important feature of theinvention is the provision of a rubber covering 3| on the rolls [8. This rubber covering 31 is made from a conventional composition and neoprene has proven especially useful in many cases. The rubber layer 31, of course, can be made from natural rubber, synthetic rubber, or rubber-like materials and'is s0 compounded and vulcanized as to be rendered heat resistant and to have a durometer hardness of between about and 95. Ordinarily only a very thin layer of rubber 31 is provided on the roll and this layer of not over about inch in thickness is bonded to the roll in a conventional manner. The bond between the roll I8 and the rubber layer 31 is facilitated by forming a set of threads 32 or 33 at each end of the metal roll 34 which forms the core of the roll l8. This metal roll 34 is of relatively thin wall thickness. intermediate its ends and has a bore 35 formed therein that has an apertured spray pipe36 extending therethrough. Then to aid in cooling the roll 34, suitable coolant is supplied a pipe 31 that connects to one end of the pipe 36 and with the other end of the pipe 3'! terminating short of the opposite end of the roll 34. A pipe 38 extends into such end of the roll 34 to exhaust the coolant collecting in the bore of the roll. A further feature of the invention is that a similar pipe 39 connects to an apertured spray pipe 4| positioned in bore 4| a formed in the embossing roll I? to convey coolant medium to such roll. The coolant is sprayed from the pipes 36 and 41 up against the upper, inner surfaces of the rolls to cool such surfaces with the fresh coolant since coolant collects in the lower parts of the bores of rolls Hand 34* and then exhausts through the-pipes 38 and'40.

A primary feature of the invention is that the the tank E9 contains a large quantity of water 42 or other suitable coolant and the roll I8 is. substantially immersed in such coolant. Thus, as the roll :8 revolves, coolant is carried up with the surface of the roll towards the pressure area of the roll is at which point the coolant layer will contact the hot themoplastic material as it passes between the rolls. This continuous supply of fresh cooled surface for the r011 133 permits the roll to be used continuously without damaging the physical roperties of the rubber layer 3! on the roll. Also, it is thought that possibly the cooling efiect of the roll it on the hot thermoplastic material plus the cooling action of the embossing roll I! facilitates keeping the embossed designs in the thermoplastic sheet as it cools. By use of a rubber back-up layer 3-l which offers a fast acting, resilient backing under the embossing pressures, the rubber roll serves to drive the thermoplastic into the embossing recesses in the roll I! but yet the rubber roll 3| forms a substantially smooth backed surface for the artificial leather sheet I4 produced by the invention. In previous types of embossing operations, the back surface of the artificial leather sheet has ordinarily been marred or scored by the embossing operation. The invention also permits a, faster embossing operation since the plastic can be embossed at calender speeds, such as 20 yards a minute.

Fig. 3 of the drawing shows that the roll l8 has a crowned portion I8a. intermediate its ends. In actual operation, the crown on 60 inch roll may be about of an inch for the entire diameter of the roll. This slight degree of crown on the roll serves to center the sheeted material on the roll and to provide suflicient pressure in the roll I8 at its center portion to drive the thermoplastic material at the center of the roll I! into the embosing recesses whereas with ordinary cylindrical rolls this desired result is not obtained. This crown on the roll [8 is all formed in the rubber coating layer on the metal roll base.

By use of the embossing rolls immediately adjacent the calender used in forming the artificial leather sheets, no reheating or reprocessing of the artificial leather is required in order to emboss same. Likewise, the apparatus and method of the invention permit continuous embossing operations by means which do not require anything more than a minimum amount of supervision and maintenance work.

Thus an eificient inexpensive embossing method and apparatus have been provided and the objects of the invention are achieved.

The specific thickness of the rubber layer used on the back-up roll will vary dependent upon.

the type of bond of the rubber to the metal core. If a conventional bond is used in uniting the rubber to the metal, the rubber layer will function excellently when A" thick. If a hard rubber base is used to secure a soft rubber surface layer to the roll, then the hard rubber layer may be to A thick and the soft layer will be about A" thick. When using the soft layer alone, it may be possible to eliminate the external cooling of the back-up roll.

In accordance with the patent statutes, one complete embodiment of the invention has been explained herein in detail but it will be understood that we are not limited to the embodiment of the invention disclosed and that the scope of the invention is defined solely in the appended claim.

What is claimed is:

Apparatus for continuously embossing a thin sheet of thermoplastic material which comprises a calender adapted to heat a thermoplastic material and to form it into thin sheets, a pair of cooperating embossing metal rolls adapted to receive in continuous operation sheeted material from said calender, one of said rolls having a hard embossed surface, the other of said rolls having a relatively thin soft rubber cover permanently attached to the outer surface thereof, said rubber cover being crowned intermediate its ends, both said rolls being hollow and being provided with spray pipes in their central por-- tion adapted to receive and spray a coolant against the inner walls of said rolls, a tank containing a fluid coolant so disposed therein relative to said rubber covered roll that the latter rotates partially emersed in said coolant and being adapted to carry said coolant on the roll surface into contact with the surface of a sheet of thermoplastic material being embossed.

JOHN K. MASON. PARK P. CRISP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 806,625 Beecher Dec. 5, 1905 1,168,629 Harrigan Jan. 18, 1916 1,591,170 Lutyens July 6, 1926 2,030,066 Jenett Feb. 11, 1936 2,218,227 Winnek Oct. 15, 1940 2,397,608 Johnson Apr. 2, 1946 

